Michael Martin has announced he is stepping down as Speaker of the House of Commons after the furore over MPs' expenses.
In a brief statement to MPs, he said he was standing down on 21 June, rather than at the next election, which has traditionally been the time at which Speakers step down.
His successor will be chosen on the following day.
Following criticism of the procedure used for Mr Martin's selection, a new, as yet untested, practice was drawn up in 2001.
As part of the new Exhaustive Ballot system, MPs will vote in secret and the whole process will take place in one day.
Candidates must be nominated by at least 12 MPs, of whom at least three must be of a different party from the candidate. Nominations must be handed in between 0930 and 1030 on the day after the Speaker quits.
The candidates would then address the Commons at 1430 - in an order determined by lots being drawn. There would then be a half hour of voting.
An absolute majority - more than 50% of those voting - is necessary before a winner can declare victory.
If no candidate has a majority, the one with the fewest votes is eliminated. MPs will continue to vote, for a number of rounds if necessary, until there is one candidate who has an absolute majority.
Sticking with tradition, the new Speaker is dragged to the Chair, feigning reluctance.
Finally, the Speaker-elect must be approved by the Queen before they may take office.
Names that have been mentioned as a potential successor include Sir George Young, Sir Menzies Campbell, Sir Alan Haselhurst and Frank Field.